Strategies for treatment are directed towards prevention of virus infection which are:

Planting virus free materials

Controlling vectors where applicable

No imports of germplasm from countries known to harbour the virus

Host plant resistance

Plants with symptoms are rogued during active growth

Procedures in case of positive test

At IITA, all lines testing positive are discarded after different diagnostic tests have been conducted. There are no economic chemical agents effective against these plant viruses. Hot water is sometimes used, but most of the time when used as seed treatment, the virus is not eliminated from the seeds and the seed quality is reduced.

If germplasm material is valuable, for import / export,the seeds are grown under containment, inspection during active growth, rogue plants with symptoms and incinerate.

Serological testing of symptomless lines by ELISA and PCR

Harvested lines found free from the virus are released to breeders and / or recommended for international distribution.

References and further reading

Naidu RA, d’Hughes J. 2001, Methods for the detection of plant viruses. In Proceedings of the Plant Virology in Sub- Saharan Africa. Conference organized by IITA, 4-6 June 2001.

Strategies for treatment are directed towards prevention of virus infection which are:

Planting virus free materials

Controlling vectors where applicable

No imports of germplasm from countries known to harbour the virus/ additional declaration that seeds for international distribution were grown in locations known to be free of the virus

Imports subjected to post entry processing on arrival

Host plant resistance

Plants with symptoms are rogued during active growth

Procedures in case of positive test at IITA

All lines testing positive are discarded after different confirmatory diagnostic tests have been conducted. Hot water has been recommended, but most of the time when used for seed treatment, the seeds deteriorate and the viuruses not eliminated

Harvest lines found free from the virus and release to breeders for research.

For export

Seeds from symptomless lines harvested from the multiplication plots meant for international distribution are grown in the screen houses.

The lines are inspected during active growth in collaboration with Plant Quarantine officials. Plants with symptoms are rougued and incinerated. Leaf samples and seeds from symptomless plants are tested serologically by ELISA or PCR

Complete loss of a cowpea crop in northern Nigeria resulting from CABMV attack under irrigated field conditions was reported by Raheja and Leleji (1974). A yield loss of 13-87% due to natural infection of cowpea by CABMV was reported in Iran by Kaiser and Mossahebi, ( 1975). While Kannaiyan and Haciwa, (1993) reported a loss 48-60% in Zambia).

Symptoms

All the plant stages and parts are affected: flowering , fruiting, seedling and vegetative stages in addition to the pods, growing points, inflorescence, leaves, seeds, stems and whole plant.Symptoms vary according to the cowpea cultivar and the existing CABMV race. Shoyinka et al., (1997) reported that CABMV symptoms observed on cowpea under field conditions were extremely variable.

Edwardson and Christie (1986) reported that CABMV infected 53 species in 28 genera of the Leguminosae. The virus is also said to infect 13 other families among which are Amaranthaceae, Aizcaceae, Chenopodiaceae, Cucurbitaceae, Hydrophyllaceae, Labiatae, Iridaceae, Leguminosae, Scrophulariaceae, Polygonaceae, Solanaceae and Pedaliaceae. Isolates from the different parts of the world have different hosts range (Bock, 1973).

Geographic distribution

The virus is worlwide in distribution. It is considered to be a major and widespread disease of cowpea through out sub-Saharan Africa (Bock, 1973; Ladipo, 1976; Thottappilly and Rossel, 1985; Burke et al., 1986

The virus has also been reported in Europe, Asia, Africa, Brazil, USA, Australia and Papua New Guinea

Harvest lines found free from the virus and release to breeders for research

For export:

Seeds from symptomless lines harvested from the multiplication plots meant for international distribution are grown in the screen houses.

The lines are inspected during active growth in collaboration with Plant Quarantine officials. Plants with symptoms are rougued and incinerated. Leaf samples and seeds from symptomless plants are tested serologically by ELISA or PCR

Atiri GI, Ekpo EJA, Thottappilly G. 1984. The effect of aphid-resistance in cowpea on infestation and development of Aphis craccivora and the transmission of cowpea aphid-borne mosaic virus. Annals of Applied Biology, 104(2):339-346.

Harvest lines found free from the virus and release to breeders for research.

For export:

Seeds from symptomless lines harvested from the multiplication plots meant for international distribution are grown in the screen houses.

The lines are inspected during active growth in collaboration with Plant Quarantine officials. Plants with symptoms are rougued and incinerated. Leaf samples and seeds from symptomless plants are tested serologically by ELISA or PCR

Harvest lines found free from the virus and release to breeders for research

For export:

Seeds from symptomless lines harvested from the multiplication plots meant for international distribution are grown in the screen houses.

The lines are inspected during active growth in collaboration with Plant Quarantine officials. Plants with symptoms are rougued and incinerated. Leaf samples and seeds from symptomless plants are tested serologically by ELISA or PCR

Harvest lines found free from the virus and release to breeders for research

For export:

Seeds from symptomless lines harvested from the multiplication plots meant for international distribution are grown in the screen houses.

The lines are inspected during active growth in collaboration with Plant Quarantine officials. Plants with symptoms are rougued and incinerated. Leaf samples and seeds from symptomless plants are tested serologically by ELISA or PCR